Conventional mechanical street sweeping vehicles that sweep up dirt and debris and ultimately deposit it into a hopper have been known for several years. They typically are manufactured on their own frame or on a truck frame, and have a pair of counter-rotating brooms disposed one at each side of the street sweeping vehicle. These counter-rotating brooms sweep dirt and debris from the edges of a road, or the like, even from against a sidewalk curb, to underneath the central area of the street sweeping vehicle. An elongate drum-shaped sweeping broom is disposed at the rear of the street sweeping vehicle and rotates about a horizontal axis to sweep the dirt and debris on the road forwardly to an upwardly inclined conveyor that receives the dirt and debris and conveys the dirt and debris into a hopper for subsequent controlled dumping from the hopper.
All known prior art conveyors used in mechanical street sweepers are belt type conveyors having a flexible conveyor belt looped around a horizontal idler shaft disposed immediately ahead of the sweeping broom, and a raised remote drive shaft, so as to present upper and lower straight spans of the conveyor belt between the two shafts. The flexible conveyor belt travels in one rotational direction only while in use. However, they are usually reversible, if necessary, for maintenance purposes.
There are two specific kinds of belt type conveyors. One kind, namely a carrying conveyor, comprises a number of spaced apart substantially rigid cleats, with each cleat disposed across the width of the conveyor belt. Dirt and debris are swept forwardly by the sweeping broom onto the bottom portion of the upper straight span of the conveyor belt, essentially adjacent the idler shaft, and are carried on the upper span of the conveyor belt to be dumped off the top end of the conveyor belt, adjacent the drive shaft, into the hopper. The cleats preclude the dirt and debris from sliding down the upper straight span of the conveyor belt.
The other kind of belt type conveyor, namely a drag conveyor, comprises a number of spaced apart somewhat flexible cleats, commonly known as "squeegees", disposed each one across the width of the conveyor belt. The carrying conveyor additionally comprises a conveyor bed disposed immediately below and parallel to the lower straight span of the conveyor belt such that the squeegees drag along the conveyor bed so as to drag dirt and debris up the conveyor bed, and push the dirt and debris off the top end of the conveyor bed into the hopper. It is necessary that the squeegees be somewhat flexible in order to make substantially sealing sliding contact with the conveyor bed, so that dirt and debris, and even mud and water, are dragged up the conveyor bed. The conveyor bed terminates at its lower end in a curved lower lip that follows the arc of the distal edge of the squeegees as they arcuately traverse the bottom end of the conveyor.
Both of the above described kinds of belt type conveyors have a number of significant problems associated with them. Dirt and debris tend to cause severe abrasion of the conveyor belts, cleats, drive chains, sprockets, bearings, elevator bed plate, and so on, thus causing these parts to wear quickly. The replacement of these parts is typically quite frequent, perhaps every few months, and is labour intensive, and therefore very expensive. Further, in carrying conveyors, it is necessary to have the bottom portion of the conveyor close to the ground in order to be properly positioned to receive dirt and debris from the sweeping broom. Therefore, carrying conveyors must have short cleats, since the cleats must clear the ground. Accordingly, such carrying conveyors cannot convey large debris, such as tire pieces, tree branches, and so on, and almost certainly jam when large debris is encountered. Some types of large debris also tend to become tangled in the sprockets, drive chains, and so on.
Further, in drag conveyors, it is necessary that the flexible squeegees be short so that they will bend only minimally when pushing a heavy mass of dirt and debris up the conveyor bed. Another problem with drag conveyors is that the metal base within the squeegee tends to bend when impacted by large or heavy objects. Once the metal base is bent, the squeegee cannot traverse around the upper and lower shafts, and must be replaced.
It is an object of the present invention to provide an apparatus for lifting dirt and debris swept forwardly by the sweeping broom and depositing the dirt and debris into a hopper.
It is another object of the present invention to provide an apparatus for lifting dirt and debris swept forwardly by the sweeping broom and depositing the dirt and debris into a hopper, which apparatus requires less frequent replacement of parts as compared to prior art conveyors.
It is another object of the present invention to provide an apparatus for lifting dirt and debris swept forwardly by the sweeping broom and depositing the dirt and debris into a hopper, which apparatus has improved wear characteristics and lower maintenance costs as compared to prior art conveyors.
It is yet another object of the present invention to provide an apparatus for lifting dirt and debris swept forwardly by the sweeping broom and depositing the dirt and debris into a hopper, which apparatus can lift large debris without jamming.
It is still another object of the present invention to provide an apparatus for lifting dirt and debris swept forwardly by the sweeping broom and depositing the dirt and debris into a hopper, the parts of which apparatus are not readily bent or otherwise damaged.